CN100394804C

CN100394804C - Image signal correction method and image signal correction apparatus

Info

Publication number: CN100394804C
Application number: CNB2005100093153A
Authority: CN
Inventors: 大泽诚司; 稻村浩平
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2004-02-19
Filing date: 2005-02-18
Publication date: 2008-06-11
Anticipated expiration: 2025-02-18
Also published as: EP1566958A2; US7447356B2; JP2005236604A; EP1566958A3; US20050185099A1; KR20060042950A; KR100664572B1; CN1658680A; JP4058420B2; EP1566958B1; DE602005023364D1

Abstract

The objective of the present invention is to enhance a specific color without changing the hue of an original image. At least two different gray-level correction functions are provided for luminance signals input for three colors, R, G and B, and these functions are used to calculate correction coefficients for the individual colors. Then, the luminance signals input for the three colors are synthesized so that the weighting of the colors is changed in accordance with the input luminance signals, and a correction coefficient is calculated that is used in common. The input signals are then multiplied by the thus obtained correction coefficient.

Description

Image signal correction method and image signal correction apparatus

Technical field

The present invention relates to a kind of in the colour-video signal that coloured image implement is proofreaied and correct is handled, suppress tone (hue) thus variation image signal correction method and image signal correction apparatus that gray scale is proofreaied and correct.

Background technology

In recent years, in the coloured image of TV etc., in order to emphasize and contrast correction sense lightness sense and tone, to carry out the occasion that the video signal correction of gray correction (gray-level correction) and colour correction etc. handles and become more and more.

As the 1st existing example of gray correction, the colored input luminance signal of reflection is implemented the protruding gray correction of input-output characteristic as shown in Figure 6 down relatively, thereby improves the contrast sense of reflection.For example, luminance signal is imported after resolving into red (R), green (G), blue (B) 3 looks.Input luminance signal at 3 looks of RGB is (R _In1, G _In1, B _In1)=(0.3,0.4,0.5), (R _In2, G _In2, B _In2)=(0.7,0.8,0.9) occasion by carrying out such greyscale transformation of Fig. 6, becomes (R _Out1, G _Out1, B _Out1)=(0.09,0.16,0.25), (R _Out2, G _Out2, B _Out2)=(0.49,0.64,0.81).The monochrome information L of image is calculated as L=0.2125R+0.7154G+0.0721B (ITU-R BT709), become L _In1=0.386, L _Out1=0.152, L _In2=0.786, L _Out2=0.620.Each is than becoming L _In2/ L _In1=0.786/0.386=2.04, L _Out2/ L _Out1=0.620/0.152=4.09, L _Out1/ L _In1=0.393, L _Out2/ L _In2=0.789, brightness descends, and contrast improves.

In addition, thus as the 2nd existing example of gray correction by implement as shown in Figure 7 input-output characteristic improve towards the gray correction of epirelief reflection the lightness sense be treated to known technology.Input luminance signal at 3 looks of RGB is (R _In1, G _In1, B _In1)=(0.3,0.4,0.5), (R _In2, G _In2, B _In2)=(0.7,0.8,0.9) occasion by carrying out such gray correction of Fig. 7, becomes (R _Out1, G _Out1, B _Out1)=(0.548,0.632,0.707), (R _Out2, G _Out2, B _Out2)=(0.837,0.894,0.949).The brightness of computed image obtains L _In1=0.386, L _Out1=0.620, L _In2=0.786, L _Out2=0.886.Each is than becoming L _In2/ L _In1=0.786/0.386=2.04, L _Out2/ _Out1=0.886/0.620=1.43, L _Out1/ L _In1=1.61, L _Out2/ L _In2=1.13, contrast descends, and brightness improves.

Yet in these prior art examples, before and after the gray correction, the ratio of RGB also changes, and has the so common problem of tone variations.

As to this way to solve the problem, there is the such technology (the 3rd prior art example of gray correction) of following patent documentation 1.

Patent documentation 1 is the such formation of Fig. 8.In Fig. 8, symbol 21 is a signal pre-treatment part, and symbol 22 is the nonlinear transformation part, and symbol 23 is the colour correction part, and symbol 24 is the signal post-processing part.In addition, the color picture signal input terminal that symbol 25 is imported for transmitting color picture signal successively, symbol 26 is the color picture signal lead-out terminal of output color picture signal.By the pre-treatment that signal pre-treatment part 21 is removed vision signals such as denoising, carry out gray correction by nonlinear transformation part 22.In addition, the output of relative nonlinear conversion fraction 22 is carried out colour correction by colour correction part 23, the processing of being undertaken after this by signal post-processing part 24.

In nonlinear transformation part, become as major part

(formula 1)

M＝max(r _in，G _in，B _in)

R _out＝f(M)·R _in/M

G _out＝f(M)·G _in/M

B _out＝f(M)·B _in/M

And output.Wherein, max () is for selecting peaked function, R _In, G _In, B _InBe the RGB chrominance signal of input, R _Out, G _Out, B _OutBe the RGB chrominance signal of output, f () is the gray correction function.

When making the following formula distortion,

(formula 2)

C?＝f(M)/M

R _out＝R _in·C

G _out＝G _in·C

B _out＝B _in·C

The ratio of RGB does not change before and after gray correction, preserves tone.

In patent documentation 1, put down in writing such formation, that is, transformed to the L of CIE (international lighting crewman meeting) from rgb signal ^*a ^*b ^*With Luv etc., only brightness composition (L ^*Or L) after carrying out gray correction once more inversion change rgb signal into.In this occasion, only the brightness composition carries out conversion, and color component does not change, so, still preserve tone.

As other known example, only also has the formation that the Y composition as one YUV signal of television broadcasting signal carries out gray correction.

In addition, as the prior art example of colour correction, such processing also is known, that is, as shown in Figure 9, making the colored input luminance signal R of reflection, each gray correction function of G, B is that (R is f to different functions relatively _r(x), G is f relatively _g(x), B is f relatively _h(x), x is for being worth arbitrarily), proofread and correct tone.For example, the input luminance signal at RGB is (R _In1, G _In1, B _In1)=(0.3,0.4,0.5), (R _In2, G _In2, B _In2)=(0.7,0.8,0.9) occasion by carrying out the such gray correction of figure, becomes (R _Out1, G _Out1, B _Out1)=(0.36,0.4,0.5), (R _Out2, G _Out2, B _Out2)=(0.84,0.8,0.9).In this occasion, and to compare before the gray correction conversion, the ratio of the R after the conversion increases, and becomes and has emphasized the red color tone color.

In addition, in following patent documentation 2, method as the selectivity correction of carrying out original image, such colour correction method is disclosed, promptly, by making up based on the weighted average correction of selecting weighted value, wherein this weighted value is with selecting look to depart from and reduce from primary colors more than or equal to 2 selectivity colour correction variation of all kinds relatively.

(patent documentation 1) Japanese kokai publication hei 06-311354 communique

(patent documentation 2) Japanese kokai publication hei 08-315132 communique

When the color of the specific scope of emphasizing to video, wish not emphasize color sometimes with not changing tone.Yet, in the different example of each the gray correction function that makes the RGB that enumerates by the prior art example of above-mentioned colour correction, tone variations.

As the method for emphasizing the color of particular range, exist use to emphasize in the color of the 3rd method of the gray correction described in the above-mentioned background technology with not making tone variations.RGB has other gray correction function respectively, carries out gray correction to having peaked color in the rgb signal, and likening to coefficient before and after the gray correction taken other color signal (Figure 10).

In Figure 10, symbol 31 is the selector of value maximum in the rgb signal value of selecting input, symbol 32 is the comparator of the output information corresponding with peaked signal in the rgb signal value with input, symbol 33 is for selecting in the gray correction data storage described later the switch of any corresponding to the output of comparator 32, symbol 34 is according to the R gray correction tables of data of exporting the gray correction data of R from the indication of switch 33, symbol 35 is according to the G gray correction tables of data of exporting the gray correction data of G from the indication of switch 33, symbol 36 is that symbol 37 is will be from gray correction tables of data 34 according to the B gray correction tables of data of exporting the gray correction data of B from the indication of switch 33,35, the gray correction data of 36 outputs are applicable to the gray correction unit of the output valve of selector 31.

Each gray correction function at RGB is the such occasion of Figure 11 (f of the content of R gray correction tables of data for being represented by solid line _r(x), the content of G gray correction tables of data is the f of dotted line _g(x), the content of B gray correction tables of data is dashdotted f _b(x)), for example, as input (R _In, G _In, B _In)=(0.7,0.3,0.5) time, judge that at comparator 32 R is maximum, is input to switch 33 with its corresponding signal.Switch 33 is selected R gray correction tables of data.In addition, selector 31 is selected the maximum 0.7 of RGB, is input to gray correction unit 37 and divider 38.Gray correction unit 37 is with reference to the checking list of R gray correction tables of data 34, to R _InProofread and correct, output to divider 38 0.9.The value 0.9 that value 0.7 before divider 38 usefulness are proofreaied and correct is removed after proofreading and correct is exported as correction coefficient 1.286.Multiplier 39,40,41 will be taken original rgb value from the correction coefficient of divider 38 inputs, output (R _Out, G _Out, B _Out)=(0.9,0.39,0.64).At this moment, R _Out: G _Out: B _Out=0.9: 0.39: 0.64=0.7: 0.3: 0.5=R _In: G _In: B _In, preserve tone.

In addition, import (R _In, G _In, B _In)=(0.5,0.7,0.3) occasion, the gray correction tables of data of maximum G, output (R are selected in action similarly _Out, G _Out, B _Out)=(0.32,0.45,0.19).R _Out: G _Out: B _Out=0.32: 0.45: 0.19=0.5: 0.7: 0.3=R _In: G _In: B _In, preserve tone.

Equally, when having imported (R _In, G _In, B _In)=(0.3,0.5,0.7) time, become (R _Out, G _Out, B _Out)=(0.3,0.5,0.7), colour brightness does not change.

That is, in this routine occasion, the brightness of the color that R is the strongest (showing red color) increases, and the brightness of the color that G is the strongest (showing green color) reduces, and the brightness of the color that B is the strongest (showing blue color) does not change.

Generally, when make with RGB in when wishing the corresponding gray correction function of the tone emphasize towards epirelief, the brightness of this tone is risen.When making the gray correction function corresponding with the tone of not wishing to give prominence to protruding down, the brightness of this tone reduces.Like this, can emphasize the color of particular range.

Yet, in this constitutes, have following such problem.Figure 12 has represented for example R, the G signal of the certain level line of display unit, from the correction coefficient of divider 38 outputs, and the brightness value on the picture.The B signal is 0 at Zone Full.As shown in Figure 12, a picture left side is maximum R, and along with turning right, the R composition reduces.In addition, in the position of the R of maximum, the G signal is 0, and along with turning right, the G composition increases, and is 0 position at the R composition, G composition maximum.At the picture middle body, just in time R equates with the value of G, is the border with it, and the left side is for showing red color, and the right side is for showing green color.

In this occasion, in the picture left-half, the R composition is maximum, so, the R gray correction function f of Figure 11 _r(x) calculation correction coefficient.Here, correction coefficient is often more than or equal to 1, and in addition, towards the right side up, correction coefficient increases.In addition, at the picture right half part, G becomes to be divided into maximum, so, by G gray correction function f _g(x) calculate correction coefficient, but correction coefficient is often smaller or equal to 1, in the lower-left, correction coefficient diminishes.The variation of brightness of this moment is such as shown, is the border with picture central authorities, occur brightness rank difference.

Summary of the invention

The present invention makes in view of above-mentioned actual conditions, and its purpose is emphasized the image signal correction method and the image signal correction apparatus of specific color with being to provide a kind of tone that does not change original image.

In order to achieve the above object, in image signal correction method of the present invention, the input luminance signal of relative 3 looks is according at least 2 different these input luminance signals of gray correction function correction; It is characterized in that: have the step of using above-mentioned gray correction function calculation of all kinds to go out the corrected value of input luminance signal of all kinds, change the step that calculates general correction coefficient of all kinds that weight ground synthesizes according to above-mentioned input luminance signal of all kinds relatively, and be multiplied by the step of stating correction coefficient at above-mentioned input luminance signal.

In image signal correction apparatus of the present invention, the input luminance signal of relative 3 looks is according at least 2 different these input luminance signals of gray correction function correction; It is characterized in that: have and use above-mentioned gray correction function calculation of all kinds to go out the correcting unit of the corrected value of input luminance signal of all kinds, change the correction coefficient calculation that calculates general correction coefficient of all kinds that weight ground synthesizes according to above-mentioned input luminance signal of all kinds relatively, and be multiplied by the multiplication unit of stating correction coefficient at above-mentioned input luminance signal.

The present invention can emphasize color with not changing tone when emphasizing the color of particular range.

Description of drawings

Fig. 1 is the block diagram of the image signal correction apparatus of embodiment 1.

Fig. 2 is the example of the gray correction function of embodiment 1.

Fig. 3 is the figure of signal that the reflection cross section of embodiment 1 is shown, correction coefficient, output brightness.

Fig. 4 is the block diagram of the image signal correction apparatus of embodiment 2.

Fig. 5 is the block diagram of the image signal correction apparatus of embodiment 3.

Fig. 6 is the example of the gray correction function of the occasion of carrying out gray correction in the past.

Fig. 7 is another example of the gray correction function of the occasion of carrying out gray correction in the past.

Fig. 8 is the block diagram of explanation gray correction in the past.

Fig. 9 carries out the example of the correction function of the occasion that color emphasizes for using the prior art example.

Figure 10 carries out the block diagram of the image signal correction apparatus of the occasion that color emphasizes for using the prior art example.

Figure 11 is used to illustrate the example of gray correction function that uses the prior art example to carry out the action of the occasion that color emphasizes.

Figure 12 carries out the concrete example of the occasion that color emphasizes for using the prior art example.

Figure 13 is the block diagram of television equipment of the present invention.

Embodiment

(embodiment 1)

(summary) will be made as R respectively to the rgb value that the reflection input luminance signal carries out obtaining after the color separation _In, G _In, B _In, the gray correction function of R is made as f _r(x), the gray correction function with G is made as f _g(x), the gray correction function with B is made as f _b(x).The ratio of the output valve (corrected value) that will obtain according to input value and the gray correction function of R is made as K _r, the ratio of the output valve (corrected value) that will obtain according to input value and the gray correction function of G is made as K _g, the ratio of the output valve that will obtain according to the input value of B and gray correction function is made as K _b, K then _r, K _g, K _bBecome respectively

(formula 3)

K _r＝f _r(R _in)/R _in

K _g＝f _g(G _in)/G _in

K _b＝f _b(B _in)/B _in

The correction coefficient C of pixel is according to these are obtained than the weighted average of having carried out with the corresponding weighting of size of importing the RGB input value relatively.That is,

(formula 4)

C = \frac{R_{in}^{2} \cdot K_{r} + G_{in}^{2} \cdot K_{g} + B_{in}^{2} \cdot K_{b}}{R_{in}^{2} + G_{in}^{2} + B_{in}^{2}} = \frac{R_{in} \cdot f (R_{in}) + G_{in} \cdot f (G_{in}) + B_{in} \cdot f (B_{in})}{R_{in}^{2} + G_{in}^{2} + B_{in}^{2}}

The correction coefficient C that this is general and this RGB input value multiply each other, and carry out gray correction.

(formation) Fig. 1 illustrates the block diagram of present embodiment.In Fig. 1, symbol 1 is the input value R of relative R _InBe suitable for the gray correction function f _r(R _In) and output R gray correction unit, symbol 2 is the input value G of relative G _InBe suitable for the gray correction function f _g(G _In) and output G gray correction unit, symbol 3 is the input value B of relative B _InBe suitable for the gray correction function f _b(B _In) and output B gray correction unit.

In addition, symbol 4 is with input value R _InWith the multiplier of the output multiplication of R gray correction unit 1, symbol 5 is with input value G _InWith the multiplier of the output multiplication of G gray correction unit 2, symbol 6 is with input value B _InWith the multiplier of the output multiplication of B gray correction unit 3, symbol 7 is the adder with the whole additions of output of above-mentioned multiplier 4,5,6.

Symbol 8 is respectively with respectively square and the whole quadratic sum calculator of additions of the input value of RGB, and symbol 9 is for removing the divider of the output of adder 7 with the output of quadratic sum calculator 8, and symbol 10 is the input value R at R _InThe multiplier of the output of multiplier-divider 9, symbol 11 are the input value G at G _InThe multiplier of the output of multiplier-divider 9, symbol 12 are the input value B at B _InThe multiplier of the output of multiplier-divider 9.

In the present embodiment, R gray correction unit 1, G gray correction unit 2, B gray correction unit 3 these 3 be correcting unit.Comprise R gray correction unit 1, G gray correction unit 2, B gray correction unit 3 interior, multiplier 4,5,6, adder 7, quadratic sum calculator 8, divider 9 are correction coefficient calculation, and finally the value from divider 9 outputs is correction coefficient C.Multiplier 10,11,12 is a multiplication unit.

Fig. 2 is the example of the input-output characteristic of R gray correction unit 1 (solid line), G gray correction unit 2 (dotted line), B gray correction unit 3 (chain-dotted lines).In Fig. 2, the input-output characteristic of R gray correction unit is towards epirelief, and the input-output characteristic of G gray correction unit is protruding down, and the input-output characteristic of B gray correction unit is linear.

In the occasion of the gray correction function that is suitable for Fig. 2, for example work as RGB input value (R _In, G _In, B _InWhen)=(0.7,0.3,0.5) being input to a certain pixel, with R _InBe input to R gray correction unit 1, output f _r(R _In)=0.9.Equally, obtain f _g(G _In)=0.14, f _b(B _In)=0.5.

These are multiplied by input value R by multiplier 4,5,6 respectively _In, G _In, B _In, add its output by adder 7.From adder 7 output R _In* f _r(R _In)+g _In* f _g(G _In)+B _In* f _b(B _In)=0.7 * 9+0.3 * 0.14+0.5 * 0.5=0.92.

In addition, in quadratic sum calculator 8, will as input value 0.7,0.3,0.5 square 0.49,0.09,0.25 addition, output quadratic sum S=0.83.

The output valve 0.92 of adder 7 is input to divider 9 with the output valve 0.83 of quadratic sum calculator 8, obtains general correction coefficient C=0.92/0.83=1.11 of all kinds.

It is taken original input value, export final output valve R _Out=C * R _In=0.776, G _Out=C * G _In=0.333, B _Out=C * B _In=0.554.This R _Out, G _Out, B _OutRatio be

Equate substantially that with the ratio of RGB before the gray correction tone does not change.

At input RGB input value (R _In, G _In, B _In)=(0.3,0.7,0.5) occasion, same, become (f _r(R _Out), f _g(G _Out), f _b(B _Out))=(0.5,0.45,0.5), the output of divider 9 (correction coefficient C) is C=(0.3 * 0.5+0.7 * 0.45+0.5 * 5)/(0.3 ²+ 0.7 ²+ 0.5 ²)=0.715/0.83=0.86.

Final output valve is (R _Out, G _Out, B _Out)=(0.258,0.603,0.431),

In the formation of present embodiment, to carry out colour correction with the same reflection of the pattern of enumerating that has problems in above-mentioned problem, as shown in Figure 3, brightness degree difference as shown in Figure 12 disappears, and brightness changes smoothly.As described above, in the present embodiment, when emphasizing the color of specific scope, do not have the rank difference of brightness, brightness is changed smoothly, can emphasize color with not changing tone.

(embodiment 2)

Fig. 4 illustrates embodiments of the invention 2.In Fig. 4, symbol 13 is no more than the amplitude limiter of the desirable maximum ground enforcement restriction of R for the output of multiplier 10, the amplitude limiter of restriction is implemented on the desirable maximum ground that symbol 14 is no more than G for the output of multiplier 11, and symbol 15 applies the amplitude limiter of restriction with being no more than the desirable maximum of B for the output of multiplier 12.Other constitutes similarly to Example 1, so, adopt same-sign, omit explanation.In the present embodiment, amplitude limiter 13,14,15 is a limiting unit.

In the present embodiment, before multiplier 10,11,12 output valves, identical with the foregoing description 1.Output C * R from multiplier 10 _InBe input to amplitude limiter 13.In amplitude limiter 13, judge that whether the value from multiplier 10 surpasses the desirable maximum (8 occasions 255) of R, as do not surpass, then will be worth directly output, as surpass, then export maximum (8 occasions 255).Amplitude limiter 14, amplitude limiter 15 are too respectively relatively from the output C * G of multiplier 11, multiplier 12 _In, C * B _InWith maximum, as not surpassing maximum, then should be worth directly output, as surpass, then export maximum.

Like this, can prevent that correction coefficient C is excessive and make output valve surpass the value of desirable maximum.

(embodiment 3)

Fig. 5 illustrates the embodiment of the invention 3.In Fig. 5, symbol 16 is the maximum value detector of maximum in the input value that detects RGB and output, symbol 17 is to export the coefficient calculator of removing the value that obtains after the desirable maximum of RGB with the output of maximum value detector 16, output and the output of coefficient calculator 17 and the comparator that a less side exported of symbol 18 for comparing divider 9.Other constitutes similarly to Example 1, so, adopt same-sign, omit explanation.In the present embodiment, maximum value detector 16 and coefficient calculator 17 are maximum value calculation unit.Comparator 18 and multiplier 10,11,12 are for comparing multiplication unit.

In the present embodiment, up to from divider 9 output valves, identical with the foregoing description 1.The input value R of RGB _In, G _In, B _InBe input to maximum value detector 16, the value that output is maximum.Be input to coefficient calculator 17 from the maximum of the RGB of maximum value detector output.The value of coefficient calculator 17 usefulness input is removed the value V of the desirable maximum of RGB _Max(8 occasions 255) output to comparator 18 with its result.Comparator 18 compares the output of divider 9 and the output of coefficient calculator 17, exports a less side's value.Be input to multiplier 10,11,12 from the value of comparator 18 outputs, take input signal R _In, G _In, B _In, obtain final output valve R _Out, G _Out, B _Out

In the foregoing description 1, when correction coefficient C surpasses V _Max/ max (R _In, G _In, B _In) time, there is R _Out, G _Out, B _OutIn any surpass V _MaxOccasion, but in the present embodiment, calculate V by coefficient calculator 17 in advance _Max/ max (R _In, G _In, B _In), compare with correction coefficient C, select a less side, so, can be no more than desirable maximum ground and carry out colour correction.

In embodiment 1～3, use (formula 4) to calculate correction coefficient C, but, then also can use any coefficient as for satisfying the correction coefficient of condition of the present invention.

In addition, in embodiment 1～3, use block diagram to be illustrated, but realize that formation of the present invention is not limited to by constituting shown in the foregoing description.

Figure 13 is the block diagram of television equipment of the present invention.Receiving circuit 20 is made of tuner and decoder etc., and receiving satellite broadcast and the TV signal, the data broadcasting by the Internet etc. of ripple etc. on the ground output to image processing section 21 with the Image Data after the deciphering.The image signal correction apparatus that image processing section 21 comprises checking gamma circuit, resolution changing circuit, I/F circuit etc. and illustrates in the above-described embodiments, the Image Data that will carry out image processing convert the display format of display unit to, and view data is outputed to display unit 25.Display unit 25 by display panel 24, drive circuit 23, and control circuit 22 constitute.The view data of 22 pairs of inputs of control circuit implements to be suitable for the signal processing of the treatment for correcting of display panel etc., simultaneously, view data and various control signal is outputed to drive circuit 23.Drive circuit 23 outputs to display panel 24 according to the view data of input with drive signal, shows video mapping.

Receiving circuit 20 and image processing section 21 can be used as set-top box (STB26) and accommodate the casing different with display unit 25, also can accommodate the casing with display unit 25 one.

Claims

1. image signal correction method, for the input luminance signal of 3 looks according at least 2 different these input luminance signals of gray correction function correction; It is characterized in that having:

Use above-mentioned gray correction function calculation of all kinds in 3 looks to go out step for the above-mentioned input luminance signal of 3 looks general correction coefficient, and

Be multiplied by the step of stating correction coefficient at above-mentioned input luminance signal,

Wherein, the above-mentioned input luminance signal of establishing 3 looks is A1, A2 and A3, and the above-mentioned gray correction function of establishing in 3 looks of all kinds is f1 (X), f2 (X) and f3 (X), and establishing above-mentioned correction coefficient is C, satisfies following equation (1):

C = \frac{A_{1} \cdot f_{1} (A_{1}) + A_{2} \cdot f_{2} (A_{2}) + A_{3} \cdot f_{3} (A_{3})}{{A_{1}}^{2} + {A_{2}}^{2} + {A_{3}}^{2}} - - - (1) .

2. image signal correction method according to claim 1 wherein also has:

State desirable peaked mode that value that correction coefficient obtains is no more than the above-mentioned luminance signal that is corrected applies restriction to above-mentioned input luminance signal step to be multiplied by at above-mentioned input luminance signal.

3. image signal correction method according to claim 1 wherein also has:

Deduct the maximum of the above-mentioned input luminance signal of 3 looks from the desirable maximum of the luminance signal that is corrected, wherein, being used for to the above-mentioned correction coefficient that the above-mentioned input luminance signal of 3 looks is taken advantage of is at the calculated value of above-mentioned correction coefficient and by less one step in the value of above-mentioned subtraction acquisition.

4. image signal correction apparatus, for the input luminance signal of 3 looks according at least 2 different these input luminance signals of gray correction function correction; It is characterized in that having:

Use above-mentioned gray correction function calculation of all kinds in 3 looks to go out correction coefficient calculation for the general correction coefficient of above-mentioned input luminance signal of all kinds, and

Be multiplied by the multiplication unit of stating correction coefficient at above-mentioned input luminance signal,

C = \frac{A_{1} \cdot f_{1} (A_{1}) + A_{2} \cdot f_{2} (A_{2}) + A_{3} \cdot f_{3} (A_{3})}{{A_{1}}^{2} + {A_{2}}^{2} + {A_{3}}^{2}} - - - (1) .

5. image signal correction apparatus according to claim 4 wherein also has:

State desirable peaked mode that value that correction coefficient obtains is no more than the above-mentioned luminance signal that is corrected applies restriction to above-mentioned input luminance signal limiting unit to be multiplied by at above-mentioned input luminance signal.

6. image signal correction apparatus according to claim 4 wherein also has:

Deduct the maximum of the above-mentioned input luminance signal of 3 looks from the desirable maximum of the luminance signal that is corrected, wherein, being used for to the above-mentioned correction coefficient that the above-mentioned input luminance signal of 3 looks is taken advantage of is at the calculated value of above-mentioned correction coefficient and by less one subtrator in the value of above-mentioned subtraction acquisition.

7. television equipment, wherein have: the image processing section that comprises the described image signal correction apparatus of claim 4, received television signal also outputs to the receiving circuit of above-mentioned image processing section with above-mentioned input luminance signal, and according to the display unit from the view data display map of above-mentioned image processing section output.